Crystallization and spectroscopic properties in Er3+ doped oxyfluorogermanate glass ceramics containing Na

• Er3+ doped oxyfluorogermanate glasses with a composition containing Na element were synthesized.
• It was confirmed that Na had significant impact on the crystallization behavior of precursor glasses.
• Depending on the annealing procedure supplied, the nanocrystals with different crystal phase were precipitated from glasses.
• The effect of nanocrystals precipitated from precursor glass on the UC luminescence of the doped Er3+ ions was analyzed.

The Er3+ doped oxyfluorogermanate glasses, with a composition containing Na element, were synthesized by the conventional melting–quenching technique. When Na element was introduced into the composition of oxyfluorogermanate glass, the crystals behavior was investigated in details. Depending on the annealing procedure supplied, thermal annealing of precursor glasses in the system GeO2/BaF2/AlF3/Na2O/NaF/ZnO/GdF3/ErF3 led to the precipitation of different crystal phase nanocrystals. It was confirmed the nanocrystals in GC600 is orthorhombic NaBaAlF6 which led to enhance obviously in the UC luminescence of Er3+. However, the nanocrystals in G585 led to decrease in the UC luminescence, which indicated few Er ions enter into the lattice of this nanocrystal phase. The reason of the decrease in UC emission intensity of GC585 was analyzed.